The present invention relates to a magnetic disk apparatus, such as a hard disk device, for example, and it relates to, in particular, a magnetic disk apparatus, being able to record servo signals on a disk without using an actuator and/or clock head of an outside, as well as, a method for recording servo patterns for it.
In general, in manufacturing processes of the magnetic disk apparatus, a number of servo signals (i.e., servo sectors) are recorded on the recording surface thereof, being several tens to a hundred or more per one (1) round, for enabling the position detection of a head on the magnetic disk rotating at a high speed.
Writing of such the servo sectors thereon, for defining the position in a circumferential direction on the disk, therefore, in normal, is conducted through a process, which is called by a “servo write”. In such the servo write process, generally, it is conducted by using an actuator and/or a clock head of an outside, for the exclusive use of the servo write.
On the other hand, without using such the actuator and/or the clock head of an outside for the exclusive use of the servo write; i.e., with using a head of itself, which is equipped within the magnetic disk apparatus, it is already known that such the servo write as was mentioned above can be conducted, by controlling the writing position in the circumferential direction on the disk, with much flexibility, in the following patent documents:
Japanese Patent Laying-Open No. Hei 8-212529 (1996);
Japanese Patent Laying-Open No. Hei 10-50014 (1998);
Japanese Patent Laying-Open No. Hei 10-222943 (1998); and
Japanese Patent Laying-Open No. 2002-319253 (2002).
However, in the case where the servo write is conducted without using the clock head for the exclusive use thereof, it is necessary to determine timing for newly writing, upon the basis of detection times of patterns when reproducing the tracks, which are recorded on the disk, before. However, a rotation of the disk includes fluctuation in the speed thereof. For this reason, looking at each of the servo sectors, separately, the disk rotation speed when the track was recorded in the past does not always coincide with that when it is reproduced thereafter. Also, this difference comes to be a cause of errors in writing in the circumferential direction on the disk, and further results into a shift in the bit phase, between the tracks neighboring to each other, or the like, thereby lowering the so-called quality of the servo signal. In particular, with the magnetic disk apparatus having a small disk diameter, an inertia of the disk as a rotating body is also small, therefore an ill influence or effect due to this speed fluctuation comes to be remarkable.